The invention relates to an instrument for cutting biological and notably human tissue, especially during endoscopic surgery, with an outer tube and a hollow, cylindrical cutting tube which is positioned within the outer tube and can be rotated about its longitudinal axis and at whose distal end at least one blade is positioned. The instrument also comprises a manipulator which is mounted at the proximal end of the tubes. The outer tube can be displaced in the axial direction of the cutting tube, which is immovably fixed to the manipulator, against the force of a pressure spring between an initial position in which the outer tube projects beyond the cutting tube on the distal side and a working position in which the blade protrudes from the distal end of the outer tube.
Surgical instruments of this kind, known as morcellators, are used in endoscopic surgical interventions that require the removal of large portions of tissue. These morcellators consist of a power-driven cutting tube, notably an electromechanically driven cutting tube, that can be directly introduced into the body or into a natural or synthetic bodily cavity. In order to remove tissue, a pincer is introduced into the body or bodily cavity to grip the tissue for extraction. When the pincer is then withdrawn and the tissue is pressed against the cutting edge of the rotating morcellator, a cylindrical block of tissue can be cut out through a prescribed pull, and possibly by varying the turning speed and turning direction, and removed through the tube. Even large amounts of tissue can be extracted in this manner within a few minutes.
A medical instrument of this general type is known from EP-A-0 621 008. With this familiar instrument, a button can be activated to move the outer tube from the initial position to the working position in which the blade of the cutting tube protrudes from the outer tube. By pressing the button, a blocking element is displaced, which allows the outer tube directly connected with the button to be withdrawn as far as the manipulator.
Because the button and the outer tube are firmly connected with one another and the button is pre-tensioned by means of a readjusting spring, the operator must hold the button down until the blade of the cutting tube remains in the working position. This circumstance limits the operator""s freedom of movement in operating this familiar instrument, since the operator must hold the button permanently pressed down during the cutting process.
In other morcellators, known from EP-B1-0 555 803 and EP-A1-0 806 183, which have a cutting tube positioned within the distal end of the outer tube protruding from the outer tube, there is the danger that the cutting area of the cutting tube is not covered, or cannot be covered, so that injuries can occur through cutting at unintended places. This risk also exists in the morcellator, known from DE-C2-44 40-035, which has a protective tube positioned inside the cutting tube.
Additional medical cutting instruments are familiar from EP-A1-0 841 036 and EP-A1 0 807 412. Both these documents show how to arrange the outer tube and the cutting tube so that they can be moved in relation to one another. The disadvantage of these familiar instruments, however, is that they both require long-term activation of the button in order to move the cutting tube into cutting position. This continuing pressure on the button clearly limits the operator""s freedom of movement.
On the basis of this familiar technology, the invention is based on the task to improve a surgical instrument of the type specified at the outset in such a way as to ensure the greatest possible freedom of movement for the operator along with simple and safe maneuverability. The solution of this task through this invention is distinguished in that the outer tube is blocked in the starting position against axial displacement by means of a blocking element which contacts the proximal end of the outer tube and can be unlocked by means of an actuator button positioned on the manipulator in such a way that the outer tube can be displaced thereafter into the working position by exerting axial pressure on the outer tube, independently of an additional activation of the actuator button, and that the pressure spring automatically returns the outer tube to the blocked starting position after each displacement into working position.
This invention""s design of the surgical instrument allows the operator the greatest possible freedom of movement because displacing the outer tube from the initial position to the working position requires only a single pressure on the actuator button in order to release the blocking element that is in contact with the proximal end of the outer tube. As soon as the blocking element is released, the operator can also release the actuator button, because displacement of the outer tube over the tissue, secured by means of a pincer instrument through the hollow, cylindrical cutting tube and pulled out to the manipulator, can also proceed in such a way that pressure is exerted on the surgical instrument by means of the manipulator, so that the surrounding outer tube clamping the tissue as a trocar sleeve is displaced into the working position in relation to the cutting tube.
As soon as axial pressure is no longer exerted on the outer tube, this outer tube is automatically returned to the initial position and is once again blocked in this position by the blocking element. No further cutting is possible until the blocking element is again released through pressure on the actuator button.
The blocking effect of the blocking element is reinforced, in addition, by the fact that the blocking element is spring-pressured in blocked position; that is, the blocking element, if it is not released by the actuator button, is automatically returned to the blocked position by means of a pressure spring. In an adaptation of the invention, the blocking of the outer tube by the blocking element is facilitated by the fact that a start incline is provided for the blocking element at the proximal end of the outer tube.
The blocking element is released, in a preferred adaptation of a surgical instrument according to the invention, by means of a pin, which is immovably fixed to the blocking element and which is housed within a curved track positioned in the shaft of the actuator button and can be displaced along the curved track through pressure on the actuator button. By means of this constrained action of the pin spring connected with the blocking element, the blocking element is displaced into unlocked position by activation of the actuator button, that is, through pressure on the housing of the manipulator.
Finally, it is proposed with this invention that the actuator button itself, against the force of a pressure spring, should be retractable into unblocked position into the housing of the manipulator, so that the actuator button is automatically restored to its initial position after each activation. Additional characteristics and advantages of the invention can be seen in the following description of the related illustrations of a model for an instrument, in accordance with the invention, for cutting biological and notably human tissue. The illustrations are as follows.